Let me preface this by saying that I realize many of you consider this topic beaten nearly to death. I have searched this forum & others and still find the answers elusive. I recently bought an '04 Ranger/2.3L/automatic/regular cab/short bed w/111.3K miles that is getting between 10 & 12 mpg around town, which seems extremely low. I'm not looking for a definitive Dr. House diagnosis; I just need guidance. The facts so far:

1. By watching the gauge and comparing it to the fuel quantity when I gas up, it seems the gauge is pretty accurate.
2. Temp is in mid-range by the little dash gauge.
3. Tires are good, pressure is good and alignment feels right w/ nothing amiss indicated on tread wear.
4. Weather is mild, so no a/c.
5. Haven't hauled anything (but a few handfuls of fallen leaves) since I bought it.
6. Seems to run very well @ all speeds and idles smoothly.
7. No outward indications of a fuel leak- no odor or wet places.
8. New air filter.
9. Starts easily, oil looks clean @ proper level, ditto trans fluid.
10. No "engine" light or other dashboard warnings.

I drive with a light foot and stay around 60 on the hiway. I understand it's a truck & not a Civic, I know the auto won't do as well as the 5-spd stick and I know that a 2.3L is a larger 4-banger than the one in my Corollla. But I also know that both my previous S-10s- at similar curb weight and with a 2.2L engine- got much better mileage around town. A couple of friends with similar Rangers report much better, also.
My reading and research leads me to suspect a sensor somewhere is outta whack, with the exhaust O2 being the first suspect.
Thoughts on what to check first?

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'04 Ranger/2.3L Auto/Regular Cab/No bells or whistles

the truck dealership for a different truck.

something is wrong a 4cyl getting 10-12mpg is just crazy.

I just bought a 97 ranger 4cyl 5sp and the first tank of gas got 21mpg with an equal mix of city/suburban/highway driving.

maybe fuel injectors,

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97 ranger 4cyl 5 sp 2wd

how are you calculating your mileage?

and is your check engine light on?

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1996 XLT 2.3T "White Lightning" 5/7 dropped, Turbo street toy
2006 FX4 Off Road, DD, work in progress
1985 XLT 2.8L 4x4 "The Black Pearl" (retired but still around)
1987 XL 2.3L 2wd R.I.P.

Trip odometer and gallons-to-fill.

No lights, no warnings. Borrowed a OBD reader and scanned, but it showed no codes stored.

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'04 Ranger/2.3L Auto/Regular Cab/No bells or whistles

What kind of traffic are you in mostly? When I drive in town and have to make a lot of stops and gos on smaller side roads I get awesul gas mileage. Maybe about 16 at worst though... Most sensors have their own check engine light.

What kind of air filter did you put in? Last time you changed your fuel filter? Spark plugs can also sometimes make a difference.

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2006 Ford Ranger XL "Dirty Girl" (Build Thread) TRADED

Beating half to death is an understatement

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GOLDIE
1999 2.5L XLT
Herculiner | Kobalt tool box | K&N Filter | 6k HID's | 31's BFG | Eagle Alloy 186s | 102'' Whip | Cobra 19 DX IV | Fabtech 3.5 Spindles | Pro Comp AAL kit | 15% Tint | Mustang Dome

Sim. sort of town driving with maybe 15% highway on a normal week, so I expect reduced mileage. But not 10-12 mpg, on a truck that seems to run great.
Hafta open up and check the AF; haven't done FF or plugs, yet. Those are on the list for immediate steps to see what helps.

I did notice that I'm runnin P215/75R15s instead of P225/70R15s, but can't see how that small diametric difference can account for much. I guess I need to suck it up and get it to someone for a full tune up, rather than trusting the folks I bought it from.
Is it possible for the exhaust O2 sensor to be sending- thus, no CEL- but sending bad data?

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'04 Ranger/2.3L Auto/Regular Cab/No bells or whistles

usually tires won't effect mileage much unless you're runnin like 32s or something. Might try cleaning your MAF, might not help much or at all but couldn't hurt... I also switched to a specter air filter and got another 3 mpg... I'd prerer k&n

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2006 Ford Ranger XL "Dirty Girl" (Build Thread) TRADED

Looked at lunch- the filter appears to be Fram (orange) or equal. Guess he was telling the truth. But may I take moment to chastise Ford for a terrible design? Why route that stiff, insulated a/c hose right over and around the AF housing, making disassembly and inspection such a chore?
Gonna look further and see if changing out wires and plugs and FF and O2 sensor and such is something I can accomplish in the driveway . . . unless I hafta dismantle the head to do that, too.

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'04 Ranger/2.3L Auto/Regular Cab/No bells or whistles

I know, it's so annoying to get too, I just pull them out and over and make it easier. O2 Sensor would be sending its own code along with a check engine light if anything was wrong with it, plus they can be VERY expensive for just winging it if youre not sure whats wrong.

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2006 Ford Ranger XL "Dirty Girl" (Build Thread) TRADED

At least $45 locally, for the cheapest one.

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'04 Ranger/2.3L Auto/Regular Cab/No bells or whistles

Id wait on that, they usually send some form of check engine light if anythings wrong with them. Used any fuel injector cleaner?

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2006 Ford Ranger XL "Dirty Girl" (Build Thread) TRADED

no do plugs, wires, air and fuel filter, and o2 sensors that stuff usually lasts roughly 100,000 a sensor can be "lazy" and not pop a code. rare but it can happen

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HAD -93' xlt supercab, 5-speed, 4wd, k&n filter,cb, fog lights
HAD-2000 Ranger Xlt 3.slow V6 4wd K&N, gibson exhaust, cb, hid's, fog lights, backup lights, interior blue lights, kenwood sub & amp, push bar, t-bar crank, frf stickers, cab lights.
NOW-00' xlt reguglar cab, 5-speed, 2wd, coil springs, "rangeriee" as my girlfriend named it , red interior led lights, and much more planned for the future!

Got a bottle- gonna pop it in at the next fill-up.

I wanna do all that but maybe the O2 sensor- getting mixed answers on that one.

Hey, I've been considering a buying a code monitor/reader- anyone have a recommendation? One that will also monitor real-time fuel usage/mileage while driving might be handy, too. ScangaugeII or Scangauge-E, maybe? They pop up at the top of Google searches, but never owned one.

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'04 Ranger/2.3L Auto/Regular Cab/No bells or whistles

I recently purchased a 2005 4.0 4x4 automatic. When I first started to drive my truck...my mileage was terrible. Then...I put in new plugs...cleaned the MAF...cleaned the throttle body...cleaned the IAC...changed the air filter...changed the fuel filter...changed the oil. Also...just put on a set of 4 Cooper Discoverer CTS tires. All these things combined made a tremendous difference in my mpg. I love my Ranger....